Space charge device



Aug. 4, 1931. ULREY 1,817,448

c 4 SPACE CHARGE DEVICE Filed Feb. 26/1925 70 Pump v I w NESSE' I INVENTOR 2%; pa /*0 fllr'cy I ATTORNEY Patented Aug. 4, 1931 DAYTON'ULREY, 0F PITTSBURGH, PMBYLVAH'IA, ASEIGNOB I9 WEQTINGEO'USE ELEG- TBIG & MANUFACTURING COMPANY,

A CGEEQMTION 0E PENNSYLVANIA.

SPAQE CHARGE DEVKGE Application med Eebruary 98, 19535. aerial Ho. urea.

My invention relates to space-current devices and particularly to space-current de-- vices containing vapors.

An object of my lnvention is to provide a 5 convenient means for introducing a vapor within an evacuated device.

Another object of my invention is to provide a convenient means for introducing an alkali metal vapor into an evacuated conga tainer.

Another object of m invention is to provide a convenient met 0d of producing an alkali metal vapor in situ within an evacuated container. 15 Another object of my invention is to provide a thermionic discharge device containing a reducing substance and a vapor of caesium metal. V

In the construction of vacuum tubes, it no has been found that the addition of certain of the alkali metals within the evacuated space improves the performance of the devlce. It appears that small quantities of the metals volatilize and produce an atmosphere at of the metal within the container. This metallic vapor atmosphere appears to aid the functioning of the device in several ways such as increasing the electron emission o the cathode. so Several ways of introducing the necessary metal have been employed. For instance, the metal has been introduced directly in thefree state, but this is dificult to do because of the difficulty of obtaining some of the metals, particularl caesium, in the free or elemental form. i nother method of introducing the metal vapor is to free it from the glass walls of the container by electrolysis, This method, however, is objectionable and is applicable only to sodium of"potassium which are contained in the ordinary glass.-

My invention provides means whereby the free alkali metal isliberated from its compounds in situ within the tube after the ev'ac uation of undesired gases and vapors has taken place. I v 1 Other objects and structural details of my invention will be apparent from the following description when read in connection with so the accompanying drawing, wherein;

The single figure is a view in vertical elevation, partially in section, of an evacuated device embodying a preferred form of my invention.

Referring to the has within it a plurality of metallic electrodes 2 mounted upona re-entrant portion 3 and a press 4. Lead" wires 5 thr ugh the press 4 serve 'to make proper connections to the electrodes 2. Surrounding the deviceis I an inductor 6 connected to a source 7 of highfrequency heating energy. Upon a convendrawing, a container 1 ient spot on the surface of the electrode which may preferably be the anode, iswelded a bit of misch-metal 8. U on the .mischmetal and thesurrounding e ectrode surface is placed a portion of alkali metal compound which may preferably be chloride, and if a vapor of caesium is desired in the device, it may be cesium-chloride.

The misch-metal 8 may electrode 2 by welding, and the cmsium chloride may be applied by painting thereon a solution in alcohol of caesium chloride. The alcohol is then allowed to evaporate,

be afixed to the leaving the solid caesium chloride behind.

The operation of afixing the misch-metal and ap lying the caesium chloride solution is prefera ly performed after the mount, comprising re-entrant portion 3 and'press 4, lead wires 5 and electrodes 2, have been assemhled. When'the alcohol has evaporated, the mount may be sealed within the container 1 and the assembly connected to an exhaust pump as indicated. The customary exhaust process may then be applied to the device and the major portion of the undesired gases and vapors t rein removed.

The high-f e uency inductor means 6 may then be slippe over the device and energized, causing thereby the development of proper heat within the electrodes 2 and the misch-metal 8. When the temperature of the electrodes and misch-metal reaches a oint which may be well below a dulhred heat, reactions begins between the alkali metal chloride and the misch-metal. This reaction consists in a displacement of the alkali metal, which may be caesium, from its chloride to form the free metal and a chloride of the misch-metal. The chloride of the misch-metal is non-volatile and remains inert within the device. Any surplus of misch-metal above that refiuired to com- 5 bine with the alkali metal c bride present, remains available to combine with oxygen and other objectionable residual gases which may remain within the container. The residue of the misch-metal, may function as 10 a getter in a manner analogous to the action which has'been found to occur with the use of other reducing substances.

The device may then be sealed ofi from the pump. When caesium chlorideis used, the

15 device then contains a quantity of free metallic caesium and a vapor ofthe metal is present in the container. This vapor is at an exceedingly low pressureand is exceedingly attenuated, whereby it does not produce gq troublesome or objectionable phenomena within the tube, butv does produce the desired efi'ects, among which 1s a marked increase in the electron emission of the cathode electrode. v v

5 The reducing agent 8 ma be the mischmetal as mentioned which is a mixture of' rare earth metals such as lanthanum, cerium, yttrium, indium and gallium. 7 Metallic 4 magnesium may be' substituted for the g9 misch-metal as may also metallic calcium,

provided the tube electrodes are notpermitted to reach as high a temperature during the evacuation process as may be permitted-when employing misch metal.

3 While I have shown but a single embodiment of my invention in the accompanying drawing, it is capable of various changes and modifications therefrom without de arting from the spirit thereof, and it is esired,

wtherefore, that only such limitations shall be 7 placed thereon as are imposed b the prior art or indicated in the appende claim.

' I claim as my invention V The method of introducing a vapor of a metallic caesium into a space charge device -which comprises attaching to a metallic electrode therein a portion 0 misch-metal, depositing thereon caesium chloride fi'om alcoholic solution, evacuating undesired vapors w therefrom, and heating to initiate a chemical reaction between the V misch-metal and the V caesium chloride, whereby free caesium metal is liberated and'volatilized, and a compound of the misch-metal and chlorine is formed.

In testimony whereof, I have hereunto subscribed my name this 20th day of February,

a a DAYTON ULREY. 

